At least 2 weeks after the completion of the last course of chemotherapy, patients receive maintenance therapy. Patients with a good response to initial therapy with prednisone receive maintenance therapy comprising oral dexamethasone three times daily on weeks 1 and 2; vincristine IV on day 2 of weeks 1 and 2; oral mercaptopurine daily on weeks 1-14; and oral methotrexate once weekly on weeks 1-14.